Existing mobile communications systems are made up of multiple wireless networks that are managed by different network service providers. There are often situations when traveling geographically, where a mobile phone, or other portable communication device, will encounter an area of network disruption. For example, the portable communication device may enter an area of no-coverage, such as within a tunnel. Likewise, as a mobile communication device moves from a region controlled by one network to a region controlled by another network, there is also the chance that there will be a period of network disruption as the two networks coordinate the handoff procedure. The handoff time can often be too long in duration to allow for seamless handoffs, wherein there is no perceivable interruption of data services for the user. The long handoff periods are not only due to signal drops, but can also be due to network access, authentication, authorization, security mechanisms and service parameter negotiations.
It has been a goal of many service providers to provide for seamless handoffs (i.e. no discernible interruption by a user) of data transfer, during network transitions. However, in practice this has proven to be quite difficult. This is partially due to problems like “blackhole” which is RF signal dropping during transition, and “ping-ponging” which is an unclear decision as to which network to connect to.
The effects of a network disruption perceived by a user can vary depending on service type and the extent of the disruption. In the case of a fully error corrected data transfer with retransmission capabilities, most disruptions will just map to a delay in the delivery of that data. In the case of voice or video data flows, however, where delay is important, error correction algorithms have a limited ability to handle lost data, and retransmission is impractical due to continuously following order sensitive data. Any disruption of a duration longer than corresponds to the levels of data currently stored on the receiving side of the communication link will result in missing or corrupted data. In the case of video this may manifest itself to the user as visible artifacts. In the case of voice it may manifest itself as an audible click or a noticeable loss of content. Worse still, large disruptions may extend beyond a communications link protocol timeout period, such that the complete data transfer process may be terminated and require to be restarted either automatically or manually. Interruptions with noticeable effects to the user, especially those requiring a manual restarting of a service, lead to significant user dissatisfaction and are one of the leading reasons users switch mobile service providers.
In addition, for some services, the data to be downloaded or streamed is time-sensitive and dynamic. That is, the data to be downloaded is not known and cannot be made available at the portable communication device until a short period before the data is desired by the user. Where multiple transactions between a user and a data service provider are required, even delays in the order of seconds can render the service unacceptable to a user.
In light of the above, it can be seen that there is a need in the industry for an improved system for reducing perceivable service interruptions to mobile communication devices during network disruptions while keeping delays small.